The invention essentially concerns transmissions for motor vehicles and, in particular although not exclusively, hybrid transmissions for motor vehicles including, on the one hand, an internal combustion drive engine and, on the other hand, an electric motor.
It should be noted, however, that the invention is not restricted to a suchlike field of application and essentially relates to gearboxes for motor vehicles comprising an actuating system acting on a movable dog engaging with a fixed dog when changing gear.
In gearboxes of this type, the actuating system uses an assistance system comprising a means of storing energy which ensures the storage of the energy derived from the actuating system when the teeth of the movable dog come into abutment against the teeth of the fixed dog for restoring it when dog-clutching or dog-declutching again becomes possible.
The displacement of the movable dog relative to the fixed dog is governed by a control system of the gearbox.
One of the problems associated with this type of gearbox is the need to satisfy oneself, as reliably as possible, that when the control system considers that the movable dog is in a dog-declutched or disengagement position, the movable dog is effectively in that position. In the event of an error, that is to say if the movable dog is in engagement with the fixed dog when the control system considers that the movable dog is in the disengagement position, the vehicle may be subjected to unintentional accelerations or decelerations.
In order to do this, the control system must have available the actual value of the disengagement limit position of the dogs, on the basis of which an increase in the displacement of the movable dog will cause a disengagement of the teeth of the dogs.
Reference may be made to documents FR 2 977 198 and FR 2 973 299, which describe a hybrid transmission architecture for motor vehicles and a corresponding method of control which utilize coupling systems, more particularly dog systems, in order to bring a primary shaft into engagement with a rotor of an electric motor or with idler sprockets for the purpose of transmitting the driving energy to the wheels by means of a differential. However, as indicated previously, in this type of transmission, the control system of the gearbox is not able to ensure, in a reliable manner, the position of disengagement of the movable dogs.